This invention relates generally to a folding knife having a blade which automatically becomes locked once moved to an extended position.
Folding knives come in two basic types. The first type includes a blade which may be moved between a closed or retracted position, substantially within the handle of the blade, and an open or extended position, extending outwardly from the handle. In this type of folding knife, the blade is not positively locked in place when in the extended position. In other words, by using some force, the blade can be moved from the extended position towards the retracted position without requiring release of a blade locking means. This type of pocket knife can be convenient for allowing the blade to be quickly opened and blade used for cutting, and then allows for the blade to be easily returned from the extended position to the retracted position. However, if care is not used in cutting with such a knife, or if the blade is used to apply force to an object in certain directions (and in particular if force is applied to the tip of the blade), the blade can inadvertently move from the open position towards the closed position, which can cause injury to the user.
The other type of folding knife includes a means for positively locking the blade once moved to the extended position. Such a locking mechanism may automatically lock the blade in the extended position, once the blade arrives at that position, or, the locking mechanism may require the user to selectively actuate the locking mechanism when the blade is desired to be locked in the open position for a particular circumstance.
Automatic locking mechanisms for locking the blade in the open position have often included an elongated lock bar pivotally connected to the backside of the blade handle. An elongated spring, such as a piano wire-type spring, may be used to urge upwardly on the rearward portion of the lock bar to force a locking tab (provided on the forward portion of the locking bar) into engagement with a notch or recess provided in the tang of the blade.
The notch in the tang is presented to the locking tab when the blade is in the extended position. In order to move the blade from the extended position to the retracted position, the locking tab is retracted from the notch in the tang by the user depressing the opposite end of the lock bar, against the upward force generated by the spring. The simultaneous depression of the lock bar in this manner with one hand, and pivoting of the blade to the retracted position with the other hand, thus allows for unlocking of the blade, and its return to the closed position.
Blade locking mechanisms which have been patented, include those disclosed in U.S. Pat. No. 5,461,786, issued to Miller; U.S. Pat. No. 4,240,201, issued to Sawby, et al.; U.S. Pat. No. 4,274,200, issued to Coder; U.S. Pat. No. 4,502,221, issued to Pittman; U.S. Pat. No. 4,670,984, issued to Rickard; U.S. Pat. No. 4,837,932, issued to Elsener; U.S. Pat. No. 5,060,379, issued to Neely; U.S. Pat. No. 5,737,841, issued to McHenry, et al.; U.S. Pat. No. 6,370,778 B1, issued to Conable; U.S. Pat. No. 5,425,275, issued to Rogers; and U.S. Pat. No. 5,111,581, issued to Collins.
U.S. Pat. No. 4,451,982, also issued to Collins, discloses a bolt action knife having a sliding bolt carried within the handle. The bolt includes a tapered forward portion for engaging the tang of the blade, once the blade is moved to the extended position. The forward end of the bolt acts as a wedge between the tang and the handle in order to lock the blade in the extended position. Unlocking of the blade requires retraction of the bolt, against the force of a spring, a sufficient distance such that the bolt clears the tang to allow the blade to be retracted.
Even in view of the foregoing designs, however, a need still remains for a folding knife having a blocking mechanism of relatively high strength and accessibility for use in automatically locking a blade upon movement of the blade to the extended position.